This application claims the priority of German patent document number 10 2007 022 820.3-15, filed May 15, 2007, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an IR jamming system for defense against missiles which are equipped with IR-sensitive homing heads.
Such missiles are a major threat to military aircraft, and increasingly to civil aircraft as well. The homing heads operate by tracking and aiming at the heat which is produced by the aircraft engines, by frictional heating of the aircraft structure, or by reflection of solar radiation on parts of the aircraft structure.
Known and established measures against IR-sensitive homing heads include decoy flares, which are ejected by the aircraft to be protected, and active IR jammers which emit a powerful beam of modulated IR power in the direction of the approaching missile.
One application for active IR jammers is to dazzle the homing head, or to saturate it, by high-power radiation. This method is very robust, but countermeasures are known which at least reduce the jamming effect.
According to a further application of active IR jammers, the aim is to produce an error in the internal target tracking algorithm of the missile by means of modulated radiation. This operates well against homing heads which carry out a time-based angle measurement, but is less effective (or is even completely ineffective) against homing heads with a fixed search field (so-called staring sensors). In the latter case, this jamming measure may even be counterproductive since it offers a powerful beacon signal for the homing head. In addition, this method results in further problems when a multiplicity of different search-head types must be engaged at the same time.
Known active IR jammers, for example the NEMESIS infrared jamming system from Northrop-Grumman, transmit a broad beam 10 with a relatively wide beam angle which is a multiple of the diameter of the missile 1 (FIG. 1). The beam diameter at distances of 1 to 2 km is typically more than 2 m. This broad jamming beam 10 ensures that a planar wave enters the homing head optics 5, where it is focused on a detector element or detector array. A simple, low-accuracy passive tracking system can be used to aim the beam for this application. However, when the missile turns away from the beam, the jamming beam is greatly attenuated, and the jamming effect is lost.